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Vulnerability · Published Mar 30, 2026 · Assigned by GitHub_M

CVE-2025-66038OpenSC: `sc_compacttlv_find_tag` can return out-of-bounds pointers

Low 3.9

In plain English

A low-severity security flaw in OpenSC from OpenSC. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)3.9Low
Exploit odds (30 days)0.3%top 78.0% of all CVEs
Exploited in the wildNo reportsCISA SSVC: poc
Attack toolingNoneno public tooling known

Official description

OpenSC is an open source smart card tools and middleware. Prior to version 0.27.0, sc_compacttlv_find_tag searches a compact-TLV buffer for a given tag. In compact-TLV, a single byte encodes the tag (high nibble) and value length (low nibble). With a 1-byte buffer {0x0A}, the encoded element claims tag=0 and length=10 but no value bytes follow. Calling sc_compacttlv_find_tag with search tag 0x00 returns a pointer equal to buf+1 and outlen=10 without verifying that the claimed value length fits within the remaining buffer. In cases where the sc_compacttlv_find_tag is provided untrusted data (such as being read from cards/files), attackers may be able to influence it to return out-of-bounds pointers leading to downstream memory corruption when subsequent code tries to dereference the pointer. This issue has been patched in version 0.27.0.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12openscno fix listedDEBIAN-CVE-2025-66038
Debian:13openscno fix listedDEBIAN-CVE-2025-66038
Debian:14opensc0.27.0~rc1-1DEBIAN-CVE-2025-66038
Ubuntu:25.10openscno fix listedUBUNTU-CVE-2025-66038
Ubuntu:26.04:LTSopenscno fix listedUBUNTU-CVE-2025-66038
Ubuntu:26.10openscno fix listedUBUNTU-CVE-2025-66038

Affected products (as reported)

VendorProductVersions
OpenSC OpenSC < 0.27.0

Weakness: CWE-126 · Vector: CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

References