Summary
AugAssign evaluation order causing OOB write within the object in Vyper
Vyper handles AugAssign statements by first caching the target location to avoid double evaluation. However, in the case when target is an access to a DynArray and the rhs modifies the array, the cached target will evaluate first, and the bounds check will not be re-evaluated during the write portion of the statement. In other words, the following code
def poc():
a: DynArray[uint256, 2] = [1, 2]
a[1] += a.pop()
is equivalent to:
def poc():
a: DynArray[uint256, 2] = [1, 2]
a[1] += a[len(a) - 1]
a.pop()
rather than:
def poc():
a: DynArray[uint256, 2] = [1, 2]
s: uint256 = a[1]
t: uint256 = a.pop()
a[1] = s + t # reverts due to oob access
Impact
A write operation targets a memory location beyond the intended buffer boundary. Typical impact: memory corruption, crash, or arbitrary code execution.
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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Frequently Asked Questions
- What is CVE-2025-27105? CVE-2025-27105 is a low-severity out-of-bounds write vulnerability in vyper (pip), affecting versions <= 0.4.0. It is fixed in 0.4.1. A write operation targets a memory location beyond the intended buffer boundary.
- Which versions of vyper are affected by CVE-2025-27105? vyper (pip) versions <= 0.4.0 is affected.
- Is there a fix for CVE-2025-27105? Yes. CVE-2025-27105 is fixed in 0.4.1. Upgrade to this version or later.
- Is CVE-2025-27105 exploitable, and should I be worried? Whether CVE-2025-27105 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-2025-27105 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-2025-27105? Upgrade
vyperto 0.4.1 or later.