How severe is GHSA-4w26-8p97-f4jp?

No CVSS score has been assigned to GHSA-4w26-8p97-f4jp yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-4w26-8p97-f4jp?

GHSA-4w26-8p97-f4jp affects the following packages: vyper (PyPI). Ecosystems affected: PyPI.

How do I fix GHSA-4w26-8p97-f4jp?

Update vyper to 0.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4w26-8p97-f4jp is resolved across your whole dependency graph.

How do I detect GHSA-4w26-8p97-f4jp in my PyPI dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vyper. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate GHSA-4w26-8p97-f4jp if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against GHSA-4w26-8p97-f4jp?

O3 pinpoints whether GHSA-4w26-8p97-f4jp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is GHSA-4w26-8p97-f4jp actively exploited in the wild?

No public exploit code has been indexed for GHSA-4w26-8p97-f4jp yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-4w26-8p97-f4jp?

GHSA-4w26-8p97-f4jp has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 40th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-4w26-8p97-f4jp?

GHSA-4w26-8p97-f4jp is classified as Out-of-bounds Write (CWE-787). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-4w26-8p97-f4jp published, and has it been updated?

GHSA-4w26-8p97-f4jp was published on February 21, 2025 and was last updated on April 9, 2025. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

GHSA-4w26-8p97-f4jp: vyper

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk40th percentile+0.19%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Blast Radius

1 pkg affected

🐍vyper

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`vyper`	all versions	0.4.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vyper. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update vyper to 0.4.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-4w26-8p97-f4jp is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-4w26-8p97-f4jp is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to GHSA-4w26-8p97-f4jp. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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 ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a.pop() ``` is equivalent to: ```vyper def poc(): a: DynArray[uint256, 2] = [1, 2] a[1] += a[len(a) - 1] a.pop() ``` rather than: ```vyper def poc(): a: DynAr

O3 Security · Impact-Aware SCA

Is GHSA-4w26-8p97-f4jp in your dependencies?

O3 detects GHSA-4w26-8p97-f4jp across PyPI dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works

GHSA-4w26-8p97-f4jp