CVE-2021-29623

Stack-memory disclosure via unchecked WebP reads

Published May 13, 2021 · Updated Aug 3, 2024

Uninitialized-memory use in Exiv2 before 0.27.4 allows context-dependent attackers to disclose stack bytes through a crafted image file. In isWebPType, an earlier failed format probe leaves the file offset advanced, and unchecked iIo.read calls leave stack buffers uninitialized before memcmp examines them. Exploitation requires a victim to process the crafted file; the reported consequence is disclosure of a few stack bytes, not code execution or service interruption.

CVSS severity3.3
Low
EPSS probability1.10%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Uninitialized-memory use in Exiv2 before 0.27.4 allows context-dependent attackers to disclose stack bytes through a crafted image file. In isWebPType, an earlier failed format probe leaves the file offset advanced, and unchecked iIo.read calls leave stack buffers uninitialized before memcmp examines them. Exploitation requires a victim to process the crafted file; the reported consequence is disclosure of a few stack bytes, not code execution or service interruption.

The record

CVE
CVE-2021-29623
Published
May 13, 2021
Updated
Aug 3, 2024
Vendor
Exiv2
Product
Exiv2
Classifications
CWE-457, CWE-908, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 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=< v0.27.4

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Exiv2 · Exiv2version=< v0.27.4

Published CVSS scores

3.6GitHub, Inc.CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:P/I:N/A:N
3.3NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/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.

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No observations available

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

Weakness, pattern, technique

CWE-457Use of Uninitialized Variable
CWE-908Use of Uninitialized Resource
T1204.002User Execution: Malicious File

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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