CVE Intelligence
Medium exploit reference

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

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.

Published Mar 30, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 0.3% (30-day exploitation probability)+3
  • Technical severity (medium)+3
  • CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
0.28%
ahead of 19% of scored CVEs · Oct 14, 2026
Affects
OpenSC
OpenSC and 1 more
CVSS base
6.8
Medium · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Proof of concept
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — github.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (OpenSC OpenSC, Opensc Project Opensc).
  2. Apply the fixed version or the patch documented under Remediation.
  3. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
OpenSC OpenSC version < 0.27.0 Vulnerable CVE Program (cve.org) e CISA ADP
Opensc Project Opensc < 0.27.0 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Physical
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.8 CVSS 3.1 Medium 0.9 5.9 nvd@nist.gov via NIST National Vulnerability Database
3.9 CVSS 3.1 Low 0.5 3.4 security-advisories@github.com via NIST National Vulnerability Database
3.9 CVSS 3.1 Low — — GitHub_M via CVE Program (cve.org) e CISA ADP
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)
Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 6.8 (NVD (NIST)) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-126

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.28%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · opensc/opensc
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 6.8
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVE published
    Mar 30, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

3 on the record

Elsewhere on this site

OpenSC
every CVE for this vendor
CWE-126
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-40510 OpenSC < 0.27.0-rc1 Stack Buffer Overflow via piv_process_history() in card-piv.c May 29, 2026
  • CVE-2026-40528 OpenSC < 0.27.0 Buffer Overrun in do_key_value() via profile.c May 29, 2026
  • CVE-2025-13763 Libopensc: opensc: multiple uses of uninitialized variable Apr 23, 2026
  • CVE-2025-66037 OpenSC: Out of Bounds vulnerability Mar 30, 2026
  • CVE-2025-66215 OpenSC: Stack-buffer-overflow WRITE in card-oberthur Mar 30, 2026
  • CVE-2025-49010 OpenSC: Stack-buffer-overflow WRITE in GET RESPONSE Mar 30, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2025-66038 is "OpenSC: `sc_compacttlv_find_tag` can return out-of-bounds pointers", rated Medium. It affects OpenSC (OpenSC); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 6.8 describes technical severity. EPSS 0.28% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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