CVE-2024-53861 is a low-severity (CVSS 2.2) CWE-697 vulnerability in pyjwt. A fix is available for pyjwt — see the affected versions and patch details below.
Issuer field partial matches allowed in pyjwt
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-53861.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
pyjwtReal-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
Summary
The wrong string if check is run for iss checking, resulting in "acb" being accepted for "_abc_".
Details
This is a bug introduced in version 2.10.0: checking the "iss" claim
changed from isinstance(issuer, list) to isinstance(issuer, Sequence).
- if isinstance(issuer, list):
+ if isinstance(issuer, Sequence):
if payload["iss"] not in issuer:
raise InvalidIssuerError("Invalid issuer")
else:
Since str is a Sequnce, but not a list, in is also used for string
comparison. This results in if "abc" not in "__abcd__": being
checked instead of if "abc" != "__abc__":.
PoC
Check out the unit tests added here: https://github.com/jpadilla/pyjwt-ghsa-75c5-xw7c-p5pm
issuer = "urn:expected"
payload = {"iss": "urn:"}
token = jwt.encode(payload, "secret")
# decode() succeeds, even though `"urn:" != "urn:expected". No exception is raised.
with pytest.raises(InvalidIssuerError):
jwt.decode(token, "secret", issuer=issuer, algorithms=["HS256"])
Impact
I would say the real world impact is not that high, seeing as the signature still has to match. We should still fix it.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | pyjwt | ≥ 2.10.0&&< 2.10.1 | 2.10.1pip install --upgrade 'pyjwt==2.10.1' |
Affected Products
pyjwtpyjwt_projectDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pyjwt, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update pyjwt to 2.10.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-53861 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.
Frequently Asked Questions
Is CVE-2024-53861 in your dependencies?
Find it across PyPI, including transitive dependencies.