YAML::Syck versions before 1.47 for Perl allow a heap use-after-free via an anchor name reused as an anchors-table key in syck_hdlr_add_anchor
YAML::Syck versions before 1.47 for Perl allow a heap use-after-free via an anchor name reused as an anchors-table key in syck_hdlr_add_anchor. In the bundled libsyck an anchor name allocated by syck_strndup is stored both as node->anchor, freed when the node is freed, and as the key in the parser's anchors table. Freeing the node frees the shared key, and a later anchor redefinition makes st_delete compare against the freed key, so st_strcmp reads freed heap memory. Anchors are a standard YAML feature and need no special flags, so this is reached on the default Load path. Any caller that runs Load or LoadFile on an untrusted document that redefines an anchor reaches the read of freed memory.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for help- Published
- Jul 16, 2026
- Updated
- Jul 17, 2026
- EPSS
- 0.2% · 5th percentile
- CWE
- CWE-416
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Report tools
Action score
31
Monitor
Low priority for now.
- CVSS
- 31 / 40 · 7.8 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- no
- Technical impact
- total
Vulnrichment: CISA's decision-tree inputs.
Affected systems
—
Versions reported by the vendor
Affected version ranges reported by the assigning authority (CPANSec). Independent of NVD's CPE analysis and usually ahead of it.
TODDR YAML::Syck
- before 1.47affected
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Alpine:v3.24 | perl-yaml-syck | before 1.47-r0 | 1.47-r0 |
| Debian:12 | libyaml-syck-perl | before 1.34-2+deb12u3 | 1.34-2+deb12u3 |
| Debian:13 | libyaml-syck-perl | before 1.34-2+deb13u3 | 1.34-2+deb13u3 |
| Debian:14 | libyaml-syck-perl | before 1.47-1 | 1.47-1 |
| openSUSE:Leap 16.0 | perl-YAML-Syck | before 1.470.0-bp160.1.1 | 1.470.0-bp160.1.1 |
| openSUSE:Tumbleweed | perl-YAML-Syck | before 1.470.0-1.1 | 1.470.0-1.1 |
Same product
toddr: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-57075YAML::Syck versions before 1.47 for Perl allow an out-of-bounds read via a signed-char lookup-table index in syck_base64dec36Monitor
- CVE-2026-57077YAML::Syck versions before 1.47 for Perl allow an out-of-bounds read via an unbounded newline scan in newline_len30Monitor
- CVE-2026-5089YAML::Syck versions before 1.38 for Perl has an out-of-bounds read29Monitor
- CVE-2026-13713YAML::Syck versions before 1.47 for Perl allow a use-after-free and double-free via an anchor node freed while still on the parser value stack24Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| alpine:perl-yaml-syck | 1.47-r0 · Alpine:v3.24 | Package registry (OSV) |
| debian:libyaml-syck-perl | 1.34-2+deb12u3 · Debian:12 | Package registry (OSV) |
| opensuse:perl-YAML-Syck | 1.470.0-1.1 · openSUSE:Tumbleweed | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
No credits in the CNA record.
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Someone with local access to the system can trigger it.
- A low-privileged account is enough.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- high · data can be read
- Integrity
- high · data or configuration can be modified
- Availability
- high · the service can be disrupted
- Attack vector
- Local
- Attack complexity
- Low
- Privileges required
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- High
- Integrity impact
- High
- Availability impact
- High
Weakness class (CWE)
CWE-416 · Use After FreeCVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
nvd-secondary
Root cause
After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.
The bug in code
The whole CWE-416 classA representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.
Vulnerable
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);Fixed
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&dev->lock);Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
MITRE has no CAPEC/ATT&CK mapping for this CWE.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- github.com/toddr/YAML-Syck/commit/44c90a109ec3215ee7ce747bd11209835e123d8b.patch
- metacpan.org/release/TODDR/YAML-Syck-1.47/changes
- www.openwall.com/lists/oss-security/2026/07/17/3
Vendor advisories and official records. Exploit/PoC links are deliberately left out.