diff --git a/models/repo.go b/models/repo.go
index 86370821d3..b0e59f26b6 100644
--- a/models/repo.go
+++ b/models/repo.go
@@ -508,8 +508,9 @@ func (repo *Repository) mustOwnerName(e Engine) string {
 func (repo *Repository) ComposeMetas() map[string]string {
 	if repo.ExternalMetas == nil {
 		repo.ExternalMetas = map[string]string{
-			"user": repo.MustOwner().Name,
-			"repo": repo.Name,
+			"user":     repo.MustOwner().Name,
+			"repo":     repo.Name,
+			"repoPath": repo.RepoPath(),
 		}
 		unit, err := repo.GetUnit(UnitTypeExternalTracker)
 		if err != nil {
diff --git a/modules/markup/html.go b/modules/markup/html.go
index 825a41dd1f..28533cdd3f 100644
--- a/modules/markup/html.go
+++ b/modules/markup/html.go
@@ -13,6 +13,8 @@ import (
 	"strings"
 
 	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
 
@@ -646,6 +648,9 @@ func fullSha1PatternProcessor(ctx *postProcessCtx, node *html.Node) {
 // sha1CurrentPatternProcessor renders SHA1 strings to corresponding links that
 // are assumed to be in the same repository.
 func sha1CurrentPatternProcessor(ctx *postProcessCtx, node *html.Node) {
+	if ctx.metas == nil || ctx.metas["user"] == "" || ctx.metas["repo"] == "" || ctx.metas["repoPath"] == "" {
+		return
+	}
 	m := sha1CurrentPattern.FindStringSubmatchIndex(node.Data)
 	if m == nil {
 		return
@@ -657,6 +662,15 @@ func sha1CurrentPatternProcessor(ctx *postProcessCtx, node *html.Node) {
 	// but that is not always the case.
 	// Although unlikely, deadbeef and 1234567 are valid short forms of SHA1 hash
 	// as used by git and github for linking and thus we have to do similar.
+	// Because of this, we check to make sure that a matched hash is actually
+	// a commit in the repository before making it a link.
+	if _, err := git.NewCommand("rev-parse", "--verify", hash).RunInDirBytes(ctx.metas["repoPath"]); err != nil {
+		if !strings.Contains(err.Error(), "fatal: Needed a single revision") {
+			log.Debug("sha1CurrentPatternProcessor git rev-parse: %v", err)
+		}
+		return
+	}
+
 	replaceContent(node, m[2], m[3],
 		createCodeLink(util.URLJoin(setting.AppURL, ctx.metas["user"], ctx.metas["repo"], "commit", hash), base.ShortSha(hash)))
 }
diff --git a/modules/markup/html_test.go b/modules/markup/html_test.go
index be7fb0efc5..66e56f71a7 100644
--- a/modules/markup/html_test.go
+++ b/modules/markup/html_test.go
@@ -17,8 +17,9 @@ import (
 )
 
 var localMetas = map[string]string{
-	"user": "gogits",
-	"repo": "gogs",
+	"user":     "gogits",
+	"repo":     "gogs",
+	"repoPath": "../../integrations/gitea-repositories-meta/user13/repo11.git/",
 }
 
 func TestRender_Commits(t *testing.T) {
@@ -30,19 +31,20 @@ func TestRender_Commits(t *testing.T) {
 		assert.Equal(t, strings.TrimSpace(expected), strings.TrimSpace(buffer))
 	}
 
-	var sha = "b6dd6210eaebc915fd5be5579c58cce4da2e2579"
+	var sha = "65f1bf27bc3bf70f64657658635e66094edbcb4d"
 	var commit = util.URLJoin(AppSubURL, "commit", sha)
 	var subtree = util.URLJoin(commit, "src")
 	var tree = strings.Replace(subtree, "/commit/", "/tree/", -1)
 
-	test(sha, `<p><a href="`+commit+`" rel="nofollow"><code>b6dd6210ea</code></a></p>`)
-	test(sha[:7], `<p><a href="`+commit[:len(commit)-(40-7)]+`" rel="nofollow"><code>b6dd621</code></a></p>`)
-	test(sha[:39], `<p><a href="`+commit[:len(commit)-(40-39)]+`" rel="nofollow"><code>b6dd6210ea</code></a></p>`)
-	test(commit, `<p><a href="`+commit+`" rel="nofollow"><code>b6dd6210ea</code></a></p>`)
-	test(tree, `<p><a href="`+tree+`" rel="nofollow"><code>b6dd6210ea/src</code></a></p>`)
-	test("commit "+sha, `<p>commit <a href="`+commit+`" rel="nofollow"><code>b6dd6210ea</code></a></p>`)
+	test(sha, `<p><a href="`+commit+`" rel="nofollow"><code>65f1bf27bc</code></a></p>`)
+	test(sha[:7], `<p><a href="`+commit[:len(commit)-(40-7)]+`" rel="nofollow"><code>65f1bf2</code></a></p>`)
+	test(sha[:39], `<p><a href="`+commit[:len(commit)-(40-39)]+`" rel="nofollow"><code>65f1bf27bc</code></a></p>`)
+	test(commit, `<p><a href="`+commit+`" rel="nofollow"><code>65f1bf27bc</code></a></p>`)
+	test(tree, `<p><a href="`+tree+`" rel="nofollow"><code>65f1bf27bc/src</code></a></p>`)
+	test("commit "+sha, `<p>commit <a href="`+commit+`" rel="nofollow"><code>65f1bf27bc</code></a></p>`)
 	test("/home/gitea/"+sha, "<p>/home/gitea/"+sha+"</p>")
-
+	test("deadbeef", `<p>deadbeef</p>`)
+	test("d27ace93", `<p>d27ace93</p>`)
 }
 
 func TestRender_CrossReferences(t *testing.T) {
diff --git a/modules/markup/markdown/markdown_test.go b/modules/markup/markdown/markdown_test.go
index 92b4f03e34..669b49367e 100644
--- a/modules/markup/markdown/markdown_test.go
+++ b/modules/markup/markdown/markdown_test.go
@@ -21,8 +21,9 @@ const AppSubURL = AppURL + Repo + "/"
 
 // these values should match the Repo const above
 var localMetas = map[string]string{
-	"user": "gogits",
-	"repo": "gogs",
+	"user":     "gogits",
+	"repo":     "gogs",
+	"repoPath": "../../../integrations/gitea-repositories-meta/user13/repo11.git/",
 }
 
 func TestRender_StandardLinks(t *testing.T) {
@@ -103,7 +104,7 @@ func testAnswers(baseURLContent, baseURLImages string) []string {
 <li><a href="` + baseURLContent + `/Tips" rel="nofollow">Tips</a></li>
 </ul>
 
-<p>See commit <a href="http://localhost:3000/gogits/gogs/commit/fc7f44dadf" rel="nofollow"><code>fc7f44dadf</code></a></p>
+<p>See commit <a href="http://localhost:3000/gogits/gogs/commit/65f1bf27bc" rel="nofollow"><code>65f1bf27bc</code></a></p>
 
 <p>Ideas and codes</p>
 
@@ -194,7 +195,7 @@ var sameCases = []string{
 - [[Links, Language bindings, Engine bindings|Links]]
 - [[Tips]]
 
-See commit fc7f44dadf
+See commit 65f1bf27bc
 
 Ideas and codes