CVE-2026-39373
published 2026-04-07CVE-2026-39373: JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by…
PriorityP432medium5.3CVSS 3.1
AVNACLPRNUINSUCNINAL
EPSS
0.29%
21.4th percentile
JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102 limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7.
Affected
3 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | python-jwcrypto | — | — |
| latchset | jwcrypto | < 1.5.7 | 1.5.7 |
| latchset | jwcrypto | 0 – 1.5.6 | — |
CVSS provenance
nvdv3.15.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
osv6.8MEDIUM
vendor_debian6.8MEDIUM
vendor_redhat5.3MEDIUM
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VulDB
latchset jwcrypto up to 1.5.6 JWE data amplification (GHSA-fjrm-76x2-c4q4 / EUVD-2026-19911)
vuldb·2026-05-05·CVSS 5.3
CVE-2026-39373 [MEDIUM] latchset jwcrypto up to 1.5.6 JWE data amplification (GHSA-fjrm-76x2-c4q4 / EUVD-2026-19911)
A vulnerability was found in latchset jwcrypto up to 1.5.6. It has been declared as problematic. This impacts an unknown function of the component JWE Handler. The manipulation results in highly compressed data.
This vulnerability is cataloged as CVE-2026-39373. The attack may be launched remotely. There is no exploit available.
It is recommended to upgrade the affected component.
OSV
JWCrypto: JWE ZIP decompression bomb
osv·2026-04-08
CVE-2026-39373 [MEDIUM] JWCrypto: JWE ZIP decompression bomb
JWCrypto: JWE ZIP decompression bomb
### Summary
The fix for GHSA-j857-7rvv-vj97 in v1.5.6 is weak in that it does not allow to fully control the amount of plaintext the receiver is willing to deal with and provides just a weak upper bound. The patch limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can craft a JWE token under the 250KB input limit that decompresses to very large data that may exceed small devices memory availability, causing Denial of Service via memory exhaustion.
Although this is technically not unbounded I do recognize that it may be too much for devices and is something that could be surprising to developers, and we can do better than that.
NOTE: the original report was sloppy (probably AI slop) and cla
GHSA
JWCrypto: JWE ZIP decompression bomb
ghsa·2026-04-08
CVE-2026-39373 [MEDIUM] CWE-409 JWCrypto: JWE ZIP decompression bomb
JWCrypto: JWE ZIP decompression bomb
### Summary
The fix for GHSA-j857-7rvv-vj97 in v1.5.6 is weak in that it does not allow to fully control the amount of plaintext the receiver is willing to deal with and provides just a weak upper bound. The patch limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can craft a JWE token under the 250KB input limit that decompresses to very large data that may exceed small devices memory availability, causing Denial of Service via memory exhaustion.
Although this is technically not unbounded I do recognize that it may be too much for devices and is something that could be surprising to developers, and we can do better than that.
NOTE: the original report was sloppy (probably AI slop) and cla
OSV
CVE-2026-39373: JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography
osv·2026-04-07·CVSS 6.8
CVE-2026-39373 [MEDIUM] CVE-2026-39373: JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography
JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102 limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7.
Red Hat
JWCrypto: python-cryptography: python: JWCrypto: Memory exhaustion via crafted compressed JWE tokens
vendor_redhat·2026-04-07·CVSS 5.3
CVE-2026-39373 [MEDIUM] CWE-770 JWCrypto: python-cryptography: python: JWCrypto: Memory exhaustion via crafted compressed JWE tokens
JWCrypto: python-cryptography: python: JWCrypto: Memory exhaustion via crafted compressed JWE tokens
A flaw was found in JWCrypto, a Python library for JSON Web Key (JWK), JSON Web Signature (JWS), and JSON Web Encryption (JWE) specifications. An unauthenticated attacker can exploit this vulnerability by sending specially crafted JWE tokens that use ZIP compression. While the input token size is limited, the decompressed output size is not validated, allowing an attacker to cause excessive memory consumption. This can lead to memory exhaustion on affected systems, resulting in a Denial of Service (DoS).
Package: ansible-automation-platform-24/lightspeed-rhel8 (Red Hat Ansible Automation Platform 2) - Affected
Package: ansible-automation-platform-25/lightspeed-rhel8 (Red Hat Ansible Auto
Debian
CVE-2026-39373: python-jwcrypto - JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. ...
vendor_debian·2026·CVSS 6.8
CVE-2026-39373 [MEDIUM] CVE-2026-39373: python-jwcrypto - JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. ...
JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102 limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7.
Scope: local
bookworm: open
bullseye: open
forky: open
sid: open
trixie: open
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-39373 python-jwcrypto: JWCrypto: Memory exhaustion via crafted compressed JWE tokens [fedora-all]
bugzilla·2026-04-08·CVSS 5.3
CVE-2026-39373 [MEDIUM] CVE-2026-39373 python-jwcrypto: JWCrypto: Memory exhaustion via crafted compressed JWE tokens [fedora-all]
CVE-2026-39373 python-jwcrypto: JWCrypto: Memory exhaustion via crafted compressed JWE tokens [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
Bugzilla
CVE-2026-39373 JWCrypto: python-cryptography: python: JWCrypto: Memory exhaustion via crafted compressed JWE tokens
bugzilla·2026-04-07·CVSS 6.8
CVE-2026-39373 [MEDIUM] CVE-2026-39373 JWCrypto: python-cryptography: python: JWCrypto: Memory exhaustion via crafted compressed JWE tokens
CVE-2026-39373 JWCrypto: python-cryptography: python: JWCrypto: Memory exhaustion via crafted compressed JWE tokens
JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102 limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7.
Discussion:
The severity of this bug is wrong, it should be low.
No attacker can cause unlimited memory exhaustion, the bug only highlighted that the amoun
Wiz
CVE-2026-39373 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 6.8
CVE-2026-39373 [MEDIUM] CVE-2026-39373 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-39373 :
Python vulnerability analysis and mitigation
JWCrypto implements JWK, JWS, and JWE specifications using python-cryptography. Prior to 1.5.7, an unauthenticated attacker can exhaust server memory by sending crafted JWE tokens with ZIP compression. The existing patch for CVE-2024-28102 limits input token size to 250KB but does not validate the decompressed output size. An unauthenticated attacker can cause memory exhaustion on memory-constrained systems. A token under the 250KB input limit can decompress to approximately 100MB. This vulnerability is fixed in 1.5.7.
Source : NVD
## 5.3
Score
Published April 7, 2026
Severity MEDIUM
CNA Score 5.3
Affected Technologies
Python
Linux Debian
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
2026-04-07
Published