CVE-2021-29444Network attack vector

Plaintext disclosure via CBC padding timing oracle

Published Apr 16, 2021 · Updated Aug 3, 2024

Observable timing discrepancy in Panva jose before 3.11.4 allows remote attackers to decrypt JWE ciphertext without the key. AES_CBC_HMAC_SHA2 decryption performs CBC decryption before rejecting an invalid HMAC tag, so padding failures produce distinguishable response times. Exploitation requires repeated chosen-ciphertext queries—about 128 calls per ciphertext-block byte—and exposes plaintext without altering data or service state.

CVSS severity5.9
Medium
EPSS probability1.24%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Observable timing discrepancy in Panva jose before 3.11.4 allows remote attackers to decrypt JWE ciphertext without the key. AES_CBC_HMAC_SHA2 decryption performs CBC decryption before rejecting an invalid HMAC tag, so padding failures produce distinguishable response times. Exploitation requires repeated chosen-ciphertext queries—about 128 calls per ciphertext-block byte—and exposes plaintext without altering data or service state.

The record

CVE
CVE-2021-29444
Published
Apr 16, 2021
Updated
Aug 3, 2024
Vendor
Panva
Product
jose
Classifications
CWE-696, CWE-208
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 16, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 3.11.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Panva · joseversion=< 3.11.4

Published CVSS scores

4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
5.9GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-696Incorrect Behavior Order
CWE-208Observable Timing Discrepancy

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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