Busybox: heap buffer overflow in wget ftp resume when the resume offset exceeds the reported file size
- Exploited
- No known exploitation
- Fix
- No fix listed
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. wget resumes an FTP download (the resume feature is used) The resume offset is more than 2 GiB larger than the file size reported by the server Plain (unencrypted) FTP is used when the attacker is on-path
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 35/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
BusyBox's wget utility contains a heap buffer overflow when resuming FTP downloads, which a malicious FTP server or an on-path network attacker can trigger by sending crafted file size data. The attacker can remotely, without logging in, but the attack needs a user to take an action, and a successful exploit could allow arbitrary code execution or crash the application.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
A flaw was found in BusyBox. When resuming a download over File Transfer Protocol (FTP), the wget utility fails to verify that the resume offset does not exceed the file size reported by the server, resulting in an integer calculation error. A malicious FTP server or an on-path network attacker can exploit this issue by returning crafted file size metadata, triggering a heap-based buffer overflow with attacker-controlled data. Successful exploitation may allow an attacker to execute arbitrary code or crash the application, resulting in a denial of service (DoS).
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure12/25Specific setups only, reachable over the network without a login
- Reach10/20Shipped in major Linux distributions
- Severity7.5/10CVSS 7.5
- No patch5/5No patch listed yet
What would change the score
- Would score about 85 if added to CISA KEV
- Would score about 80 if CISA's SSVC rates exploitation active
What to do
Check whether your setup matches what the bug needs.
wget resumes an FTP download (the resume feature is used) The resume offset is more than 2 GiB larger than the file size reported by the server Plain (unencrypted) FTP is used when the attacker is on-pathWorkaround: The facts give no workaround. The stated conditions depend on resuming plain FTP downloads with wget, so avoiding resumed plain-FTP transfers is the only limit the facts directly support until a fix is available.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-124747 (Busybox: heap buffer overflow in wget ftp resume when the resume offset exceeds the reported file size), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-124747 (entry last updated 2026-11-10): Affected: - Red Hat Red Hat Enterprise Linux 6: version range not reported - Red Hat Red Hat Hardened Images: version range not reported Fixed versions: none listed yet. Conditions (all must be true for the bug to be hit): - wget resumes an FTP download (the resume feature is used) (source: https://access.redhat.com/security/cve/cve-2026-124747) - The resume offset is more than 2 GiB larger than the file size reported by the server (source: https://bugzilla.redhat.com/show_bug.cgi?id=2569520) - Plain (unencrypted) FTP is used when the attacker is on-path (source: https://bugzilla.redhat.com/show_bug.cgi?id=2569520) Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, no login, a user action. CISA KEV: CVE-2026-124747 is not listed as of cve.now's last read. This KEV status is for CVE-2026-124747 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://bugzilla.redhat.com/show_bug.cgi?id=2569520 - https://access.redhat.com/security/cve/CVE-2026-124747 - https://access.redhat.com/security/cve/cve-2026-124747 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-124747 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-124747.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- busybox
Version range not reported
- busybox
Version range not reported
Evidence 4
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Write-ups · 1
Establishes: Technical detail and context.
- Report
Other links · 1
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-124747
Is CVE-2026-124747 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
When wget resumes a plain FTP download and the resume offset is more than 2 GiB larger than the file size the server reported, wget fails to verify the offset. This causes a heap buffer overflow, which the advisory says may allow an attacker to execute arbitrary code or crash the application.Source: access.redhat.com, bugzilla.redhat.com
Am I affected, and how do I check?
The product entries list Red Hat Enterprise Linux 6 and Red Hat Hardened Images without version ranges. The condition is wget resuming an FTP download whose offset exceeds the reported file size by more than 2 GiB, and the advisory notes the risk is greater when an on-path attacker is present and plain FTP is used. A reader can check whether they have the wget package installed and whether scripts use wget's resume option with ftp:// URLs.Source: access.redhat.com, bugzilla.redhat.com
How do I fix CVE-2026-124747?
The facts do not name a fixed version or an updated package, so no upgrade target can be given. Check the Red Hat advisory for a fixed package for each listed product.Source: access.redhat.com, bugzilla.redhat.com
What if there's no patch?
The facts give no workaround. The stated conditions depend on resuming plain FTP downloads with wget, so avoiding resumed plain-FTP transfers is the only limit the facts directly support until a fix is available.Source: access.redhat.com, bugzilla.redhat.com